Measurement of individual compounds with detection
limits up to ppb level in soil and groundwater
The standard MIP probe with soil conductivity measurement (EC) for stratigraphy indication:
All MIP probes are equipped with a EC-dipole to measure soil electrical conductivity. As the probe is advanced, a current is applied to the electrodes and the corresponding voltage is measured. Electrical conductivity (mS/m) can be calculated and is logged with depth (1.5cm interval). The electrical conductivity of the soil is influenced by: soil particle distribution, mineralogy and the characteristics of the pore liquid. Sand-sized particles of covalently bonded minerals, such as quartz, mica, and feldspar, are generally nonconductive. Clay-sized particles, such as phyllosilicates, humic substances, and iron/manganese oxides and oxyhydroxides, tend to be highly conductive due to their extremely small size, relatively high surface area per unit/volume, and charge characteristics. Comparison of EC logs with other hydrogeologic data demonstrates that higher EC values generally reflect fine-grained material, whereas lower values indicate coarser sediments. Electrical conductivity, however, can be significantly affected by additional factors, most notably fluid chemistry and moisture content.
EC measurements are logged and visualized in the field during probing, providing the EnISSA-MIP operator/consultant useful data enabling adjustments of the research strategy (i.e. dynamic sampling) and limiting the risk to perforate impermeable layers.
The MIP-CPT probe for soil classification according to local fricion and cone resistance
The combined MIP-CPT probe has an added CPT sub to measure cone resistance and local friction together with the standard EnISSA-MIP parameters. This type of probes is pushed into the soil at constant speed without hammering by a 20 ton push truck or an anchored direct push rig. Typically, the cone resistance is high in sands and low in clays, and the friction is low in sands and high in clays. Based on the CPT measurements, soils can be classified in 12 categories (Robbertson 1986).
The MiHPT probe: a combination of MIP with the Hydraulic Profiling Tool (HPT).
The Hydraulic Profiling Tool (HPT) uses a water pump and pressure transducer to inject a constant water flow in the subsurface. The injection pressure is an indication of the local permeability of the soil. A real-time detailed pressure and flow log is generated for each probing location giving more insight in hydrogeology. Combined with dissipation tests or groundwater level data, an Estimated conductivity (K [m/day]) can be calculated based on an empirical model.
All probes can be driven into the subsurface using a Geoprobe direct push rig ( anchoring necessary for CPT). CPT-MIP can also be performed with a 20 ton CPT truck.